The invention relates to a medical instrument for separating tissue and cartilage from a body.
One kind of such instruments, so-called shaver blades, is known from U.S. Pat. No. 4,811,734. For this purpose, the distal end of the outer shaft is guided to the operating site where the tissue that is to be separated is located. To separate the tissue, the inner shaft is moved in rotation by means of an external or internal drive. As they rotate, the cutting edges formed on the inner shaft cooperate in a cutting action with a border, designed as a cutting edge, of a window of the outer shaft. The cutting edge of an opening of the inner shaft runs past the cutting edge of the window in the outer shaft on each rotation. In order to ensure that the tissue to be separated is brought between the interacting cutting edges, the inner shaft can be connected to a vacuum source whose suction effect reaches through the inner shaft as far as the window on the outer shaft, in order to suck the tissue to be separated through the window into the shafts, such that the cutting edges can separate the tissue. By means of the vacuum, the separated tissue is sucked through the hollow inner shaft and thus carried away from the operating site.
Another kind of such instruments is a curette. Particularly in arthroscopy, relatively solid areas of cartilage lie below the cutaneous tissue and, in the event of cartilage defects, have to be removed down to the bone.
In autologous chondrocyte transplantation for the regeneration of cartilage, it is necessary for the defect margins to be extremely sharply defined. This is necessary in order to ensure that an implant placed on the defect site can fuse permanently onto these defect margins.
A curette is a shaft-like instrument which, at its distal end, has a laterally protruding peripheral separating edge. The contour and the size of the separating edge are chosen such that they can surround the defect site. The curette is penetrated into the cartilage tissue as far as the bone. The curette is provided centrally with an opening through which, by means of a spatula, the tissue and cartilage pieces that have been separated within the peripheral separating edge of the curette can be shaved off and removed. It is hard to avoid so-called debridement, i.e. where separated pieces of cartilage are released into the joint, which then necessitates irrigation of the joint in order to remove the small pieces, called chips. In the case of a relatively large defect site, the diameter of the curette is then correspondingly large.
Attempts have already been made to design a curette of this kind as a suction curette. However, the pieces of cartilage separated by the curette then always have to be smaller than the suction cross section of the instrument, since otherwise the suction cross section is blocked by the pieces of cartilage. Accordingly, the suction channel would then need to have a correspondingly large diameter, which is not feasible in defect sites with diameters of a few centimeters, since such a large amount of space is unavailable in operations on joints. Such a curette is known from WO 2004/037095 A2.
As already mentioned, these interventions are in most cases minimally invasive procedures. Two different instruments have to be brought to the operating site in succession, first a shaver blade, and then a curette, followed by irrigation of the joint.
It is object of the present invention to develop a medical instrument for separating tissue and cartilage, which instrument can be used more easily and more effectively to separate tissue and cartilage.